This invention relates to improvements in and relating to switching mechanisms and in particular switching mechanisms for the control of electrical circuitry, especially that relating to a sensor such as a thermal log.
The term "electrical" is used throughout this specification, including the claims, to encompass any circuit incorporating any type of electrical or electronic components including solid state, discrete and integrated circuit components.
Thermal logs are used for sensing, measuring and recording ambient temperatures over a period of time. They can therefore provide a record of ambient temperatures experienced by perishable goods stored in containers, during a period of transit or storage.
There are, however, a number of difficulties and disadvantages associated with the use of these devices.
Thermal logs are for example susceptible to interference, whether intentional or unintentional. This creates problems with respect to the reliability of the thermal records they provide. Difficulties then arise as to which party, seller, purchaser, shipper or, insurance company, should bear the loss when goods arrive, or are retrieved, in a perished condition after a period of transit or storage.
Further, thermal logs presently available do not indicate if the goods have been subjected to ambient temperatures outside their critical temperature range. Also, if the refrigeration of goods fails for a period during transit or storage and the goods are subsequently re-frozen, it might be some time before the temperature record is known.